﻿398 
  ACTHSTOPTERYGII. 
  

  

  specimen, 
  are 
  preserved 
  on 
  each 
  side, 
  though 
  somewhat 
  

   fractured, 
  as 
  shown 
  in 
  fig. 
  5 
  ; 
  and 
  part 
  of 
  the 
  supra- 
  

   maxillary 
  plate 
  (fig. 
  5, 
  s.moc.) 
  is 
  also 
  exhibited 
  overlapping 
  

   the 
  hinder 
  end 
  of 
  the 
  maxilla. 
  The 
  anterior 
  end 
  of 
  the 
  

   alveolar 
  border 
  of 
  the 
  dentary 
  bone 
  of 
  the 
  mandible 
  

   (fig. 
  5, 
  d.) 
  appears 
  sinuous 
  in 
  side 
  view, 
  and 
  the 
  most 
  

   anterior 
  teeth, 
  which 
  are 
  enlarged, 
  are 
  directed 
  slightly 
  

   forwards. 
  Within 
  the 
  mouth 
  remains 
  of 
  the 
  pterygo- 
  

   palatine 
  arcade 
  are 
  observed 
  above 
  (fig. 
  5,pt.), 
  but 
  it 
  is 
  not 
  

   possible 
  to 
  distinguish 
  the 
  elements 
  ; 
  on 
  its 
  inner 
  face 
  

   there 
  is 
  a 
  crowd 
  of 
  minute 
  denticles 
  (probably 
  entoptery- 
  

   goid) 
  which 
  gradually 
  become 
  a 
  little 
  enlarged 
  below, 
  while 
  

   on 
  the 
  oral 
  margin 
  (probably 
  ectopterygoid 
  and 
  palatine) 
  

   there 
  are 
  large 
  teeth 
  irregularly 
  arranged 
  and 
  spaced, 
  the 
  

   largest 
  being 
  near 
  the 
  anterior 
  end. 
  When 
  viewed 
  from 
  

   within, 
  the 
  dentary 
  exhibits 
  the 
  usual 
  thickened 
  alveolar 
  

   border, 
  this 
  in 
  its 
  hinder 
  portion 
  roofing 
  the 
  space 
  occu- 
  

   pied 
  by 
  the 
  meckelian 
  cartilage. 
  The 
  splenial 
  element 
  is 
  

   also 
  conspicuous, 
  and 
  may 
  consist 
  of 
  more 
  than 
  one 
  portion. 
  

   As 
  shown 
  in 
  a 
  fragment 
  from 
  the 
  left 
  side 
  a 
  thickened, 
  

   lenticular 
  portion 
  of 
  this 
  element 
  (fig. 
  5 
  a, 
  spl.) 
  enters 
  

   the 
  mandibular 
  symphysis, 
  and 
  bears 
  at 
  least 
  one 
  large 
  

   tooth 
  immediately 
  behind 
  the 
  enlarged, 
  forwardly 
  pointing 
  

   teeth 
  of 
  the 
  anterior 
  end 
  of 
  the 
  dentary. 
  Posteriorly 
  on 
  

   the 
  inner 
  face 
  of 
  the 
  left 
  mandibular 
  ramus 
  a 
  thin 
  laminar 
  

   bone 
  (fig. 
  5, 
  spl. 
  ?), 
  bearing 
  minute 
  granular 
  teeth, 
  is 
  

   crushed 
  upon 
  the 
  dentary 
  in 
  such 
  a 
  way 
  as 
  to 
  suggest 
  its 
  

   forming 
  the 
  inner 
  wall 
  of 
  the 
  cavity 
  for 
  the 
  meckelian 
  

   cartilage. 
  Another 
  specimen 
  still 
  in 
  Mr. 
  Leeds' 
  private 
  

   collection 
  exhibits 
  the 
  same 
  plate 
  continued 
  forwards 
  

   above 
  in 
  a 
  long 
  slender 
  process 
  ; 
  it 
  is 
  thus 
  probably 
  to 
  be 
  

   identified 
  as 
  a 
  hinder 
  splenial. 
  There 
  is 
  nothing 
  worthy 
  

   of 
  remark 
  in 
  the 
  remains 
  of 
  the 
  pectoral 
  arch, 
  but 
  one 
  of 
  

   the 
  pectoral 
  fins 
  (fig. 
  6) 
  is 
  interesting. 
  The 
  three 
  fore- 
  

   most 
  rays, 
  successively 
  increasing 
  in 
  length, 
  are 
  fused 
  

   together, 
  and 
  their 
  thickened 
  proximal 
  end 
  (fig. 
  6 
  a) 
  

   exhibits 
  a 
  hollowed, 
  circular, 
  articular 
  facette 
  (/.). 
  The 
  

   other 
  rays 
  are 
  closely 
  adpressed 
  and 
  unjointed 
  so 
  far 
  as 
  

   preserved, 
  while 
  their 
  proximal 
  ends 
  simply 
  clasp 
  the 
  

   basal 
  cartilages. 
  A 
  few 
  very 
  fine 
  tubercles 
  ornament 
  the 
  

   sharp 
  anterior 
  border 
  of 
  the 
  fin, 
  and 
  similar 
  tubercles 
  are 
  

   observed 
  on 
  parts 
  of 
  the 
  other 
  rays. 
  Among 
  fragments 
  

  

  

  